This invention relates generally to automatic tool-changing machining centers, and more particularly, to a high speed toolholder for rotatably driving a high speed cutting tool from the machining center spindle at a speed several times greater than the machining center spindle speed.
Substitution of automatic tool changing, computer numerically controlled (CNC) machining centers, such as are well known in the art, in place of conventional, manually operated single purpose machine tools for the low and midvolume production of machined parts results in increased part productivity. By substituting automatic tool changing CNC machining centers for conventional single purpose manually operated machine tools, uniform part production can virtually be assured because each part can be machined precisely in accordance with a single computer program. Further, by employing automatic tool changing machining centers for production of machined parts, different machining operations can be completed on a single part without the need to manually change the tools or transfer the part to another machine, thus allowing more parts to be produced in a given period of time. Since automatic tool changing machining centers can operate unattended for long periods of time, little or no direct supervision is required, thereby reducing direct labor costs.
Present day automatic tool changing machining centers have a rotary driven spindle which is configured to receive a wide variety of cutting tools, thereby permitting completion of various types of machining operations. To prevent radial and axial spindle deflection caused by high cutting forces, the spindle of such automatic tool changing machining centers is typically made very stiff both radially and axially. High spindle stiffness results in a high static and dynamic frequency which are also very desirable. Typically, the physical size of the spindle is fixed in accordance with the type of tooling used. Large, slow speed cutting tools require a large spindle capable of transmitting a large torque while resisting high axial and radial forces. Conversely, small high speed cutting tools require a smaller spindle capable of rotating at high speeds without generating excessive heat. Heretofore, a single machine tool spindle has not been configured which can utilize both large, slow speed cutting tools and small, high speed cutting tools. To accommodate both types of cutting tools, it is heretofore been necessary to utilize two spindles, a main large, slow speed spindle for accommodating large, slow speed cutting tools and a second, smaller high speed rotary driven tool carrying spindle which is typically stored in the machine tool spindlehead adjacent to the main spindle. When high speed machining is desired, the high speed spindle is loaded from its storage position into the main spindle by a spindle change arm separate from the tool change arm which transfers the large, slow speed cutting tools between the tool storage magazine and the main spindle. While the above described arrangement facilitates the use of both large, slow speed cutting tools and small, high speed cutting tools, it is subject to disadvantage that machine complexity and costs are increased due to the need for a separate spindle, and a separate spindle change arm for transferring the high speed spindle from its storage position to the main machine tool spindle.
In contrast, the present invention concerns a high speed toolholder capable of being stored in the machine tool storage magazine and being handled by the automatic tool changer for driving a small, high speed cutting tool from a large, slow speed spindle at a speed several times greater than the spindle speed.
It is an object of the present invention to provide a toolholder for driving a small, high speed cutting tool from the large, slow speed spindle of a machine tool.
It is another object of the present invention to provide a toolholder for driving a small, high speed cutting tool from the large, slow speed spindle of a machine tool at a speed several times greater than the spindle speed.
It is yet another object of the present invention to provide a toolholder capable of being stored in the tool storage magazine and being handled by an automatic tool changer for driving a small high speed cutting tool from the large, slow speed machine tool spindle at a speed several times greater than the spindle speed.